DOI: 10.5176/2251-3353_GEOS13.25
Authors: Giuseppe Onorevoli and Enzo Farabegoli
Abstract: We simulated for the first time the palaeogeographic evolution of three thin depositional sequences of the shallow marine western Palaeotethys, deposited in the Southern Alps (SA,
Italy) during the devastating end-Permian extinction. The simulation is calibrated by a rich set of published field data measured in the uppermost Bellerophon Formation–lowermost Werfen Fm. Data and palaeogeographic maps are located in the palinspastically restored SA area. The employed software is a
preliminary version of SIMSAFADIM-CLASTIC that simulates: a) the spatial distribution of terrigenous and clastic carbonate, b) the fossil content, c) the microbial content. The models (maps) were realized as a back-analysis, by calibration with the 3D architecture of real sedimentary sequences, particularly on the spatial distribution of terrigenous-clastic carbonate ratios. The simulation covers a period of about 70 kyr, whereas each sedimentary sequence corresponds to a time-span of 15-20 kyr; the low-stand tract spans 5-6 kyr. Models that best match reality were achieved by using a curve of sea level changes obtained empirically. The maximum sea level change is about a dozen metres; the study area underwent local short periods of emersion, represented by soil or intertidal carbonates, followed by shallow marine, foreshore facies. The sea level change curve is likely to represent the global reference. We interpret results of the model by the hypothesis that the curve of sea level change presented here could have been produced by alternating global warming and cooling of the oceans. This curve, obtained by an independent method, would be utilized as an important constraint on the numerical global models of coupled atmosphere–ocean circulation. On the contrary, the disappearence of Permian-type taxa (fusulinids, foraminifers, bivalves and algae) pre-dating the P-T boundary does not match the field data because the software lacks a few specific functions; these biologic carbonate components seem to have beeen substituted by a still-unknown environmental cause producing oolites and carbonates of microbialitic origin.
Keywords: modeling, process simulation, carbonates, finite elements, SIMSAFADIM, P-T boundary, palaeogeography, Southern Alps
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